Decoding the mystery behind rainbow film on your tea
Sometimes, on the surface of tea, you can observe a delicate film that can shimmer like a rainbow. It's no wonder that the appearance of colours in a cup may raise suspicions. Where do they come from, and what does it mean?
Foaming tea and the film on its surface are phenomena that often cause concern. However, their causes are usually simple and not a reason for worry. They may look unusual, but there's nothing dangerous about them. It's worth knowing where they come from, and there are ways to prevent them. This is a fun fact you can impress your mother-in-law with during afternoon tea.
Where does the rainbow film on tea come from?
The film that appears on the surface of tea differs from the film we know from milk, with its sheen resembling spilled gasoline. It is the result of the interaction of tea polyphenols with calcium carbonate present in the water (especially hard water).
The harder the water, the more visible the film will be on the tea. You can avoid it by filtering the water before brewing the tea. Adding a slice of lemon will also help reduce the risk of this film forming. The film may look unsightly, but it is not harmful to health and does not significantly affect the flavour of the brew.
Foam in tea
Besides the rainbow film on the surface of tea, foam may also appear. There are several reasons for this phenomenon, and one of them is saponins. These are natural chemical compounds found in tea leaves and are responsible for creating foam. Saponins are harmless to our bodies, and the foam created with their involvement is not a cause for concern.
The way tea is poured also affects its foaming. If we pour tea with a strong stream from a height, we introduce more air into the drink, which escapes during brewing in the form of foam. Sometimes, this is even desirable, as in the case of Moroccan tea, which is deliberately poured from a great height.
The type of tea leaves also matters in the formation of foam. Small, loose leaves contain more air, which "escapes" after pouring the tea with boiling water, resulting in foam. This remains a harmless phenomenon that does not affect the taste and properties of the drink.
